Vehicle evaporative emissions control systems may be configured to store fuel vapors from fuel tank refueling and diurnal engine operations, and then purge the stored vapors during a subsequent engine operation. The fuel vapors may be stored in a fuel vapor canister, for example. In an effort to meet stringent federal emissions regulations, emission control systems may need to be intermittently diagnosed for the presence of sources of undesired evaporative emissions that could release fuel vapors to the atmosphere.
One method of testing for the presence of undesired evaporative emissions in an emission control system may include applying a vacuum to a fuel system and/or evaporative emissions that is otherwise sealed. An absence of gross undesired evaporative emissions may be indicated if a threshold vacuum is met. In some examples, the fuel system and/or evaporative emissions system may be sealed subsequent to the threshold vacuum being reached, and an absence of non-gross undesired evaporative emissions may be indicated if a pressure bleed-up is less than a bleed-up threshold, or if a rate of pressure bleed-up is less than a bleed-up rate threshold. Failure to meet these criteria may indicate the presence of non-gross undesired evaporative emissions in the fuel system and/or evaporative emissions system. In some examples, an engine intake manifold vacuum may be used as the vacuum source applied to the emissions control system.
However, if the vehicle is in motion when such a test is conducted, any fuel slosh events in the fuel tank of the vehicle may result in the generation of fuel vapor which may adversely impact the pressure bleed-up portion of the test. Alternatively, to avoid fuel slosh events, such a test may be conducted at an engine idle condition. However, for an engine system disposed in a hybrid electric vehicle (HEV), such tests may be avoided due to engine idle in a HEV being an inefficient operating condition. Furthermore, the advent of start/stop (S/S) technology where the engine is shut down in response to vehicle speed and/or engine torque requests being below predetermined thresholds reduces engine idling conditions, thus limiting opportunity to conduct tests for undesired evaporative emissions that rely on engine intake manifold vacuum while the vehicle is stopped. Still further issues with conducting such tests while the vehicle is stopped include irregular engine idle durations. For example, in a case where an evaporative emissions test is initiated when the vehicle stops at a traffic light, if the traffic light changes prior to completion of the test, then the test may undesirably have to be aborted. Such issues may impact completion rates for tests for integrity of vehicle fuel systems and/or evaporative emissions systems.
Toward this end, U.S. Pat. No. 9,890,744 teaches systems and methods for conducting a test for undesired evaporative emissions that include evaluating a projected route responsive to receiving a cruise control signal, and initiating the test responsive to selected entry conditions being met. In this way, tests may be initiated under situations where it may be likely that the test may be completed without being aborted. However, such an approach may be prone to a variety of issues that may adversely impact such a test. For example, while the vehicle is in motion with cruise control set, changes in traffic conditions such as congestion, unexpected lane changes of other nearby vehicles, etc., may result in cruise control being disabled. In response to cruise control being disabled, the test for undesired evaporative emissions may be undesirably aborted.
The inventors herein have recognized the above-mentioned issues, and have developed systems and methods to at least partially address them. In one example, a method comprises adjusting evacuation of a fuel system and an evaporative emissions system of a vehicle in order to conduct a test for a presence or an absence of undesired evaporative emissions stemming from the fuel system and/or the evaporative emissions system, in response to a status of a traffic light that the vehicle is approaching. In this way, evacuation of the fuel system and the evaporative emissions system to conduct the test may be performed in such a way as to enable the test to provide results without being aborted due to the traffic light status.
In one example, adjusting evacuation of the fuel system and the evaporative emissions system may include evacuating the fuel system and the evaporative emissions system via a negative pressure with respect to atmospheric pressure that is communicated to the fuel system and the evaporative emissions system from an intake manifold of an engine. Yet, in another example, adjusting evacuation of the fuel system and the evaporative emissions system includes evacuating the fuel system and the evaporative emissions system via a pump positioned in the evaporative emissions system.
In another example, adjusting evacuation in order to conduct the test for the presence or absence of undesired evaporative emissions may include retrieving the status of the traffic light via wireless communication between a controller of the vehicle and a roadside unit corresponding to the traffic light.
In another example, adjusting evacuation of the fuel system and the evaporative emissions system may further include controlling evacuation of the fuel system and the evaporative emissions system in order to reach a threshold negative pressure in the fuel system and the evaporative emissions system at a time that coincides with the vehicle coming to a stop at the traffic light. As an example, in response to the threshold negative pressure being reached in the fuel system and the evaporative emissions system, the fuel system and the evaporative emissions system may be sealed. A pressure bleed-up may be monitored in the sealed fuel system and evaporative emissions system to indicate the presence or the absence of undesired evaporative emissions stemming from the fuel system and/or the evaporative emissions system while the vehicle is stopped at the traffic light.
As another example, the method may include maintaining current vehicle operating conditions without adjusting evacuation of the fuel system and the evaporative emissions system in response to an indication that the vehicle is predicted to pass through the traffic light without stopping.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.